Over the last several years significant progress has been made in food or beverage containers having metal tops openable without a separate opener. These are often referred to as ring tab containers since they characteristically have a ring-like metal handle which is secured to the container top by an integral rivet in the top. Usually, the handles are pivotable upward by bending of a central arm secured to the rivet, and by applying localized pressure on a partially die cut section of the container top. The handle partly severs the opening section and allows the opening section to be pivoted inward into the container, leaving an opening for consuming the liquid contents. The ring and opening section remain attached to the top. Typically the openings are pear or radially triangular shaped and are designed to provide a large enough opening for liquid contents to be drunk. In the case of dry foods, the ring not only opens the perforation but is often used to remove the entire central portion of the lid by allowing the user to pull on the ring causing perforation of a spiral path terminating at the rim and the ultimate removal of the container top.
The ring tab containers which I have just described have proven far superior to earlier designs in which the ring and tab were entirely removed from the container. The discarded rings and tabs caused significant environmental pollution and injury.
With the ring and tab remaining as parts of the container, that problem has been eliminated. The tab portion remains within the can out of reach and the ring is folded back into its original position so as to avoid interference with the user when consuming the contents of the can.
In my co-pending application, Ser. No. 569,952, filed Jan. 11, 1984, I have disclosed a new form of container opening for use in disposable plastic covers for beverage containers. Basically, I have discovered that enhanced flavor and convenience for the users is accomplished when the opening in a drink through lid is in the shape of an arc segment or as termed a "smile" extending partially around the periphery of the cup lid. I have found that for both hot and cold liquids for spreading of the beverage into a thin sheet which flows directly over the front part of the tongue provides not only greater convenience for the drinker but also enhanced flavor. Recognizing the physiology of the human mouth and taste buds, this becomes clear that all sweet beverages such as soft drinks are desirably introduced into the front region of the tongue. In the case of hot beverages whether sweet or tart, the spreading of the beverage into a thin sheet prevents scalding of the sensitive taste buds and enhances any sweet flavor present. In my co-pending application I have disclosed and claimed an improved plastic lid having such features.
It was apparent to me that the same principle needed to be applied to containers for beverages other than the plastic disposable cup lids and that ring tab metal containers are suitable for the application for my "smile" opening.
Unfortunately, the formation of a "smile" shaped drinking opening in metal container using a ring tab device is not simply accomplished.
In the prior art, containers having pear or radially triangular shaped openings, the localized pressure applied to the partially die cut part of the container easily severed the remaining thickness and allowed the tab to be opened and folded inward. A thin smile shaped opening was not conducive to even opening by such conventional ring tab designs.